The invention relates generally to environmental test chambers. In particular, the present invention relates to environmental test chambers for thermal and humidity cycling of components. The invention is especially adapted for use in testing electronic components, but may find other applications.
Environmental test chambers are frequently utilized in order to test a variety of devices. Electrical components, and in particular, computer hard drive data storage units are normally tested in an environmental test chamber in order to assure that the hard drive can operate under pre-selected temperature and humidity conditions frequently encountered during its use.
In one common design, an environmental test chamber used to test computer hard drives includes a housing having a main or first chamber, and an auxiliary or second chamber separated by a partition. The hard drives are stacked within the first chamber in a pre-selected array. The central processing units, or CPU's, responsible for controlling the operation of the hard drives, are positioned within the second chamber. The CPUs and hard drives are maintained in electrical connection by one or more electrical cables passing through the partition.
One common type of partition that may be used to separate the chambers is composed of a plurality of foamed polymeric or ceramic bricks, provided with throughholes dimensioned to enable an electrical cable to pass therethrough. Alternatively, the electrical cables may be passed through the interstitial areas between the bricks. The partition attempts to provide a sealed wall between the chambers such that the temperature and humidity conditions of one chamber does not alter the temperature and humidity conditions of the other chamber.
In operation, the first chamber is loaded with hard drives in a pre-selected spatial arrangement, while the CPUs are placed in the second chamber and separated from the main chamber by the partition. The hard drives positioned within the first chamber are exposed to an airflow of varying temperature and humidity, according to a pre-selected temperature and humidity schedule. Specifically, the treated air is introduced to the first chamber through an exhaust area, is drawn through and about the hard drives, and is evacuated therefrom at an intake area. Once evacuated from the interior of the first chamber, the air is treated to assure that the air re-entering the first chamber conforms to the preselected temperature and humidity schedule. Thereafter, the air is recirculated to the first chamber. The control units, or CPUs, positioned in the secondary chamber are maintained at room temperature, or slightly above, and normal humidity conditions so as not to overheat. During testing, the CPUs command the hard drives to execute certain operations in order to verify acceptable performance of the hard drives under varying temperature and humidity conditions.
One problem frequently encountered by existing environmental test chambers is inadequate, non-uniform airflow through the first chamber. The purpose of environmental testing is to determine whether a particular unit, such as an electrical component, will operate in a sufficient manner under preselected temperature and humidity conditions. Consequently, in order to determine whether the unit actually performs sufficiently under the preselected criteria, each unit should receive approximately the same airflow so that it experiences the preselected temperature and humidity conditions. However, existing environmental test chambers often experience airflow gradients within the first chamber. These airflow gradients, in turn, generate thermal and humidity gradients. Failure to establish a uniform airflow throughout the first chamber results in ineffective and inaccurate testing of the hard drives or other electrical components positioned within the environmental test chamber.
Additionally, most environmental test chambers are provided with an electrical control panel chamber which supports the electrical devices and circuitry necessary to operate the environmental test chamber. In most circumstances, this control panel chamber is carried by the housing and is external to both the first chamber and the second chamber. Given the elevated temperatures at which environmental test chambers are operated, the control panel chamber often becomes hot, and must be supplied with a quantity of ambient air to cool the electrical devices. The ambient air is drawn into the control panel chamber through a separate air intake assembly from that which draws ambient air into the second chamber to cool the CPUs. An air exhaust assembly evacuates air from the control panel chamber. The control panel chamber air exhaust assembly is also separate from the air exhaust assembly governing the removal of air from the second chamber. The necessity for two separate air intake and exhaust assemblies is inefficient and increases manufacturing and operation costs.
Still another problem confronted by the industry is the inability of existing environmental test chambers to provide an effective barrier or partition between the first chamber and the second chamber. As the partition is usually a plurality of tiles or bricks stacked in a vertical array, interstitial spaces between these bricks enables the migration of air between the chambers. As a result, the humid, heated air, or cooled air, positioned within the first chamber will escape into the second chamber, resulting in deleterious consequences. First, increased humidity levels within the second chamber may damage the CPUs. Furthermore, migration of air to and from the first chamber generates a thermal and humidity gradient in proximity to the partition and consequently reduces the effectiveness of any test conducted therein.
Accordingly, there exists a need for an environmental test chamber capable of providing a uniform airflow through the first chamber. There is also a need for an environmental test chamber which can efficiently draft both the control panel chamber and the second chamber, and also, provide a sealed barrier between the first chamber and the second chamber.